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Other names Di-μ-hydrido-tetrahydridodigallium
CAS number 12140-58-8
Molecular formula Ga2H6
Molar mass 145.494 g/mol
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Digallane is a chemical compound of gallium and hydrogen with the formula Ga2H6. The eventual preparation of the pure compound, reported in 1989, [1] [2] was hailed by N N Greenwood as a "tour de force".[3] Historically digallane had been reported as early as 1941 by E. Wiberg[4], however this was not verified by later work by N.N Greenwood and others.[5]



A two stage approach proved to be the key to successful synthesis of pure digallane. Firstly the dimeric monochlorogallane, (H2GaCl)2 (containing bridging chlorine atoms this can be formulated as (H2Ga(μ-Cl))2) was prepared via the hydrogenation of gallium trichloride, GaCl3 with Me3SiH. This was followed by a further reduction with LiGaH4, solvent free, at −23°C to produce digallane, Ga2H6, in low yield.

Ga2Cl6 + 2Me3SiH → (H2GaCl)2 + 2Me3SiCl
(H2GaCl)2 + LiGaH4 → Ga2H6 + LiCl

Digallane is volatile and condenses at −50°C to give a white solid.

Structure and bonding

Electron diffraction measurements of the vapour at 255°K show the structure of digallane to be similar to that of diborane with 2 bridging hydrogen atoms.[2] The terminal Ga-H bond length is 152pm, the Ga-H bridging is 171 pm and the Ga-H-Ga angle is 98°. The Ga-Ga distance is 258pm. The NMR spectrum of a digallane solution in toluene shows to peaks attributable to terminal and bridging hydrogen atoms.[2]
The solid appears to be polymeric, and on the basis of its vibrational spectrum is possibly tetrameric (i.e. GaH3)4.[2] There are terminal, non-bridging, hydrogen atoms which contrasts with α-alane, a high melting, relatively stable polymeric form of aluminium hydride, where all hydrogen atoms are equivalent and the aluminium atoms are 6 coordinate.


Digallane decomposes at ambient temperatures:

2GaH3 → 2Ga + 3H2

The reactions with Lewis bases are similar to those of diborane. With trimethylamine 1:1 and 2:1 adducts are formed i.e. NMe3.GaH3 (NMe3)2.GaH3. With phosphine a 1:1 adduct PH3.GaH3. The trimethylamine adducts have been known for some time. [6] [7] They were prepared by the reaction of LiGaH4 with trimethylammonium chloride, Me3NHCl, the 2:1 adduct is formed at low temperatures:

LiGaH4 + Me3NHCl → LiCl + H2+ Me3N.GaH3

The structure of Me3N.GaH3 was reexamined and it has been confirmed to be monomeric in both the gas and solid phases. In this it contrasts with the corresponding alane adduct, NMe3.AlH3 which in the solid is dimeric with bridging hydrogen atoms. [8] A range of other 1:1 adducts have been prepared and their stabilities determined. [9]


  1. ^ Anthony J. Downs, Michael J. Goode, and Colin R. Pulham (1989). "Gallane at last!". Journal of the American Chemical Society 111 (5): 1936 - 1937. doi:10.1021/ja00187a090.
  2. ^ a b c d Pulham C.R., Downs A.J., Goode M.J, Rankin D.W.H. Roberson H.E. (1991). "Gallane: Synthesis, Physical and Chemical Properties, and Structure of the Gaseous Molecule Ga2H6 As Determined by Electron Diffraction". Journal of the American Chemical Society 113 (14): 5149 - 5162. doi:10.1021/ja00014a003.
  3. ^ N.N. Greenwood (2001). "Main group element chemistry at the millennium". J Chem Soc Dalton Transactions: 2055 - 2066. doi:10.1039/b103917m.
  4. ^ Wiberg E.; Johannsen T. (1941). "Über einen flüchtigen Galliumwasserstoff der Formel Ga2H6 und sein Tetramethylderivat". Naturwissenschaften 29 (21): 320. doi:10.1007/BF01479551.
  5. ^ Shriver, D. F.; Parry, R. W.; Greenwood, N. N.; Storr, A,; Wallbridge, M. G. H. (1963). "Some Observations Relative to Digallane". Inorg. Chem. 2 (4): 867 - 868. doi:10.1021/ic50008a053.
  6. ^ N. N. Greenwood, A. Storr, and M. G. H. Wallbridge (1963). "Trimethylamine Adducts of Gallane and Trideuteriogallane Gallane, (CH3)3NGaH3". Inorg. Chem. 2 (5): 1036 - 1039. doi:10.1021/ic50009a036.
  7. ^ D. F. Shriver, C. E. Nordman (1963). "The Crystal Structure of Trimethylamine Gallane, (CH3)3NGaH3". Inorg. Chem. 2 (6): 1298 - 1300. doi:10.1021/ic50010a047.
  8. ^ Brain P.T., Brown H.E., Downs A.J., Greene T.M., Johnsen E, Parsons S, Rankin D.W.H, Smart B.A, Tang C.Y. (1998). "Molecular structure of trimethylamine–gallane, Me3N·GaH3: ab initio calculations, gas-phase electron diffraction and single-crystal X-ray diffraction studies". J. Chem. Soc., Dalton Trans (21): 3685. doi:10.1039/a806289g.
  9. ^ Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Digallane". A list of authors is available in Wikipedia.
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